Production of perfluorochloroolefins



J. W. JEWELL yPRODUCTION 0F PERFLUOROCHLOROOLEFINS March l0, 1959 2Sheets-Sheet 1 Original Filed Oct. 30. 1953 NN www 9 s w AT'raR/VfysMarch 10, 1959 J. w. JEWELL 2,877,275

PRODUCTION OF' PERFLUOROCHLOROOLEFINS Original Filed Oct. 30, 1953 2Sheets-Sheet 2 United States Patent O PRODUCTION FPERFLUoRoCHLoRooLEFINs Joseph Warren Jewell, Summit, N. J., assignor, bymesne assignments, to Minnesota Mining and Manufacturing Company, St.Paul, Minn., a corporation of Delaware Original application October 30,1953, Serial No. 389,206. Divided and this application October 26, 1956,Serial No. 618,536

4 claims. (Cl. 26o-653.5)

quately controlled side reactions occur resulting inthe production ofundesirable by-products with a consequent greater liability tocontamination of the monomer and to the qualityof the polymer product.In the polymerization reaction, poor temperature control results in theproduction of a polymer having an indeterminate N. S. T. and a widemolecular weight distribution. One of the principal objects of thisinventiony is to overcome the disadvantages discussed above.

It is another object of this invention to provide a process foreiiciently'separating polymer from a monomer-polymer slurry orsuspension. v v

Itis another object of this invention, tol provide a continuous processfor the production of pertluorochloroolefinl polymers, such astriiluorochloroethylene of controlled quality fromperfluorochloroparafiinic starting materials such astriuorotrichloroethane.

quantity of promoter and the bomb and contents were l f maintained at atemperature of about -'-'17 C. for about 7 days after which `thereaction was complete. The bomb was then heated at reduced pressure todistillot unreacted monomer. Polymer was removed from'the bomb in theform of a porous-plug which was subsequently pulverized and preparedvfor shipment.

While the bomb-type of polymerization results in high yields ofv polymerbased on monomer charged, and while thequality of the produced polymeris exceptionally high, certain disadvantages are inherent in the`process. Thus, the maximum diameter which may be used is about 6 inchesbecause of the poor heat=transfer through the mass to the wall. Even ina 6 inch diameter reactor the temperature dierential between the outsideof the bomb and the center is about C. Because of the limited size ofthese reactors, accompanying labor charges are high.

To overcome the disadvantages of the mass-bulk type of polymerization,continuous processes have been developed. For example, in a typicalcontinuous process for the production of polytrifluorochloroethylene,triuorotrichloroethane is dehalogenated in an auto-clave type reactor toproduce triiluorochloroethylene which is then passed through a series ofpurication steps.l -The puried triiluorochloroethylene is thenintroduced into an auto-clave type polymerization reactor together witha quantity of promoter. The polymer is formed as a suspension or slurryin the monomer.'v This monomerpolymer slurry is then separated byfiltration or centrifu" The monomer is recycled, and the polymer isygation. stored for Ifurther processing.

While present continuous polymerization processes have, to a largeextent, overcome the disadvantage-s of the mass-bulk type process, thereare still certain inherent' It is another object of this invention, toprovide a coni tinuous process for the production of polymers of'trilluorochloroethylene wherein adequate time temperature control maybe eifected. Y

Another object of this invention, is to provide animproved method forproducing monomer.

Another object of this invention is to provide an improved method -forpolymerizing monomer by controlling the concentration of reactants. Astill further object of this invention is to provide any integratedcontinuous process for the production of monomer, the polymerization ofthe monomer Vto produce solid polymer of con trolled quality and thekrecovery of the unreacted mono-- V mer from solid polymer product. l

vtion costs by providing a continuous polymerization A further object ofthis invention is to provide a` process for large capacity continuousproduction of normally solidpertluorochloroolen polymers of above' 220C. N. S.T. f t f Another object of this' invention is to reduceproducprocess.

Various other'objects and advantagesof th"prese`nt invention will beapparent to'those skilled inthe art'iroml the accompanying descriptionand disclosure.

In general, the above objects are accomplished, and

the monomer-polymer slurry into an elongated tubular drying zone',wherein heat is applied, thereby vaporizing the monomer and leaving thesolid polymer as a dispersed powder in the monomer vapor. t 1

f' This invention is applicable to the polymerization ofperuorochloroolens such as',` trifluorochloroethylene,"ydiuorodichloroethylene and 2,3 d'ichloroperuorobutene.

(CF3CC1CC1CF3) and in addition, tothe copolymerization ofperfluorochloroolens with other uorine-containl ing oleiins such asperiluorobutadiene, vvinylidene `fluoand at leastone chlorine 'atom oneach of ltwo adjacentI ride, diuoroethylene, triuoroethylene,perliuorostyrene, perfluorocyclobutene, and phenyltriiiuoroethylene. Theperlluorochlor'oolens to whichv this. inventiony is applicable, areperhaloolefns with any degree of 'unsatura` tion consisting of fluorinefrom two to fourcarbon atoms and at least one chloriner atom permolecule. The per-'- uorochloroparathnic starting materials are"perhaloparains consisting of liuorine, fromtw'o to fourcarbon atoms andatv least 'three' chlorine atoms per molecule carbon atoms. Theconditions of polymerization ofthe copolymers of theperliuorochlorooleiins are substantially the same as for thehomopolymer. The following discussion of the general application of thepresent invention to polymers of triiluorochloroethylene'applisi-'substantially to all polymerization systems with theperiiuorochloroolens. The term polymer includes homopolymers andcopolymers; the term polymerization includes liomopolymerization andcopolymerization.

In order to more clearly illustrate the process of the present inventionreferencel will be made to Figures 1 and 2 of the drawing whichdiagrammatically illustrates a suitable arrangement of apparatus inelevation which is used for the production of normally solidthermoplastic polymers of tritluorochloroethylene. The principalpieces.of equipment for effecting the process of this invention are shown inFigurel 1 of the drawing. They are dechlorination reactor 14, settler17, polymerization reactor 82, and ash dryer 92'. Thel adaptation of theuse of the flash drying apparatus in an auto-clave type process is shownin Figure 2 of the drawing. The process will be described in the drawingfor the polymerization of triuorochloroethylene to produce thehomopolymer thereof.

According to Figure 1 of the drawing and the process illustrated,trifluorotrichloroethane, commercially available as Freon 113, is passedthrough conduit 11 into preheater 12. A slurry of metallic zinc inmethanol is simultaneously introduced into preheater 12 through conduit11 by means not shown. Although zinc is a preferred dechlorinating agentother metals may be used such as tin, manganese, magnesium and ironwithout departing from the scope of this invention. Methyl alcohol is apreferred solvent although other suitable solvents, such as ethanol,butanol, propanol, glycerol, dioxane and the cello-solves may be used.The function of preheater 12 is to mix the reactants and to bring themto reaction temperature so as to initiate the reaction. Preheater 12,4is maintained at a temperature between about 75 C. and about' 250 C.,preferably between about 90 C. and about. 180 C. In a preferred methodof operation the reactants pass from preheater 12; which is maintainedat a temperature of at least about 10 C. above the temperature of thedechlorination reactor preferably about 30 C. above the temperature ofthe dechlorination reactor through conduit 13 into dechlorinationreactor 14 Where the dechlorination is effected with -accuratetemperature control. Dechlorination reactor 14 consists of either apacketed pipe or a spiral coil in a bath with a fairly steep down owpitch throughout its length. The steep down ow -pitch is necessary tomaintain the metallic dehalogenating agent, which has quite a highsettling ratein suspension. From the horizontal, the anglev of thereactor is maintained at about a minimum of 59 to a maximum of about 90.Preferably, the angle is maintained between about 20 and about 60 fromthe horizontal. Velocity of the reactants thorugh the reactor ismaintained between about 0.5 and about l feet per second preferablybetween about. 2 feet and about 6. feetper second. At a velocity lessthan about 0.5 foot per second the zinc settles andthe reaction can notlbe properly controlled. Both the time and temperature control in thisreactor arev exceptionally good particularly when the reactor is used inits preferred form, that is as a sectionally jacketed pipe, since asectional construction permits a change in the degree of cooling foreach section. Reaction temperature is maintained within a desired rangebetween about 0 C. and about 200 C. with pressure controlled as desiredso as to maintain liquid phase between about atmospheric and.

about 300 pounds per square inch gage. Preferred temperature is betweenabout 40 C. and about 175 C. with a particularly suitable temperature ofbetween about 50 C. and about 150 C. Residence time in the reactor isbetween about 3 seconds andabout 4 minutes. Produced monomer, zincchloride, methanol and any other products of the reaction are removedfrom reactor 14 through conduit 16 to settler 17. Heat exchanger 18 islocated on conduit 16 to regulate the temperature ofY they stream into.the: settler; Temperature in the: settler-is adjusted, i. e., betweenabout and about 130 C. preferably between about C. and about 120 C. sothat monomer will pass overhead through conduit 19 to cooler 20 where itis condensed and accumulated in accumulator 22. The unreacted zincconcentrate suspended in methanol and containing zinc chloride iscollected at the bottom of settler 17 and may be recycled throughconduit 23 to preheater 12. Complete elimination of monomer from thisstream while desirable, is not essential. A small fraction of thisstream may be withdrawn through line 10 to control the concentration ofheavy impurities, zinc so withdrawn may be recovered. Zinc chloride andmethanol are removed through conduit 24 where they may be recovered orrecycled. A portion of the monomer contained in accumulator 22 isrecycled through conduit 25 as to control the quality of the product.

The monomer contained in accumulator 22 is contaminated with smallquantities of methanol and other impurities from the dechlorinationzo-ne, such as trifluoroethylene,v -diuorovinyl chloride, etc. In orderto remove these impurities, the monomer is passed through conduit 26 bymeans of pump 27 into the top of waterwash tower 28. In the water-washtower, the monomer ows downward through an upward moving stream of waterwhich scrubs the-monomer free of water-soluble impurities such asalcohol. Water containing methanol and a small amount of monomer isremoved from thef top ofthe water-wash tower through conduit 31 and isvpassedy into the top portion of separator 32. Water and methyl alcoholare removed from the bottom of separator 32 through conduit 33 and maybe either discarded or' circulated to an alcohol recovery system.

Monomer containing water is passed toI dryer 34 through conduit 35;Dryer 34 contains a lconventional drying, agent, such as calciumlsulfate. then recycled through conduit 36 to absorber 37 then tocompressor 33v where it is compressedvand passed through conduit 39through cooler 41 into `accumulator 22 through conduit 42. Absorber 37serves to remove corrosive materials which might damage compressor 38.The water-washed monomer, free of Water-soluble impurities is removedfrom the bottom of tower 28 through conduit 43 to dryers 44 and 46.Dryers 44 and 46 contain a conventional drying agent such as calciumsulfate. Valves 47, 48, 49 and 51 are used to close down either of thedryers for cleaning purposes.

The dry monomer containing low and high boiling impurities from thedechlorination zone is passed to distillation column 52 through conduit53. 'Ihe temperature of distillation column 52 is maintained at about 50C. by means of reboiler 54 so that low boiling impurities are removedoverhead in vapor phase. The low boiling impurities which are removedoverhead as vapor are passed through conduit 57 to accumulator 56.Cooler 58 is a conventional cooler. A portion of the low boilingimpuritiesV is recycled to the top of distillation-column 52 throughconduit 59 as reflux. The low boiling impurities may be recovered forother use or discarded as liquid through conduit 61 or as vapor throughvalve 62 which valve is used to control the pressure in the system.

The monomer free of low boiling impurities is removed as a liquidl fromthe bottom of distillation column 52 through conduit 63 and is passed tothe center portion ofl distillation column 64. The monomer is introducedinto column64 by means of valves 66 and 67. The temperature indistillation column 64 is so adjusted asy to remove monomer as avaporous fraction overhead leav-l ing the high boiling impurities suchas diuorovinyl chloride as ay bottoms product. Temperature control iseffected by reboiler 68 which is maintained at about 52 C. The highboiling impurities are removed from column 64 as a bottoms productthrough conduit 69 and may be either recovered or discarded.Substantially pure monomer is removed asv a vapor from the: topv of.column The dried monomer is' 'acetyl peroxide. preferred. The promoteris introduced at at least one and about v through the coil is betweenabout 0.1 foot and about 10 64 through conduit 71 and is collected inaccumulator 72. Cooler 73 is a conventional cooler and is used to'condense vaporized monomer. A portion of the pure monomer contained inaccumulator 72 is recycled through conduit 73 to the top of column 64 asreflux. f

Purified monomer is passed from accumulator 72 through conduit 74 toaccumulator 75 where it is held prior to introduction into thepolymerization zone. Exchanger 77 is a conventional unit which is usedto bring the monomer to proper temperature for the desired pressure inaccumulator 75. In order to maintain this equilibrium vaporized monomerleaves accumulator 75 through conduit 78 and enters condenser 79 whereit is condensed and recycled through conduit 81. Condenser 79 andconnecting lines maintain monomer in accumulator 75 under its vaporpressure at the operating temperature.

Monomer is withdrawn as required from accumulator 75 and is introducedinto polymerization reactor 82 through conduit 83. Polymerizationrreactor 82 consists of a series of coils situated in an annular tankcontaining any suitable liquid for the purpose of temperature control. Arefrigeration coil not shown in the diagram is used to maintain thedesired temperature of the liquid in which the coil is immersed andforced circulation of this liquid is used to assure uniform temperatureand predictable transfer rates. A suitable promoter such astrichloroacetyl peroxide is introduced into the reactor from promoterstorage tank 84 through conduit 86. Other organic peroxide promoters maybe used such as benzoyl peroxide, vtrifluoroacetyl peroxide,dilluorochloroacetyl peroxide, chloroacetyl peroxide and dichlorouoro-The halogenated acyl peroxides are point preferably a plurality ofpointsalong the length of the reaction coil. The continuous injection ofpromoter at a plurality of points in a small cross section flowingstream gives a much better assurance that all the monomer has animmediate opportunity to contact the promoter than is possible when thepromoter is injected into av large volume of monomer in an autoclave.This procedure provides an added method of controlling the quality, thatis the molecular weight distribution of the produced polymer sincepromoter concentration affects the quality of the polymer. Obviously,

this type of control is not possible in an auto-clave type reactor. Fromthe horizontal, the angle of the reactor coils is maintained between aminimum of about 1 and a maximum of about 30, preferably between'about 5The velocity of the reactants passing feet per second with aparticularly suitable velocity of -between about 0.1 foot and about 5feet per second, and

a preferred velocity between about 0.73 foot and about 4 l feet persecond. Temperature in the polymerization zone is maintained betweenabout C. and about 150 C.

depending o n the promoter employed and the dimension 'through reactionzones of short length. -While approximately 25% of the monomer may beconverted to polymer within the polymerization reactor,

it is preferred to keep the concentration of polymer suspended inmonomer, between about 3 and about 12%.

The monomer stream containing suspended particles of ,polymer is passedfrom polymerization reactor 82 lthrough conduit 91 to flash dryer 9 2,Flash dryer 92 consists of an elongated tubular heater contained in a ljacketthrough which by means of lines 140 and 141, a

heating medium such as steam is circulated so as to maintain atemperature between about 60 C. and about 250 C. preferably betweenabout 80 C. and about 120"` C. The slurry of polymer` in liquid monomeris vl,adlnittedto the dryer through pressure reducing and to about 200feet per second at the outlet.

control valve 9 6. With the reduction in pressure and application' ofheat the monomer vis vaporized very rapidly. The consequent increase involume results in a rapid increase in -velocity which preventsvaccumulation of polymer on the heating surface. The relative increase invelocity is from 0.5-10 feet per second at the inlet Conditions shouldbe adjusted, i. Le., Iby using a higher temperature or a smaller pipediameter so that the minimum outlet velocity is about 50 feet persecond, preferably between about and about 300 feet per second and stillmore preferably between 150 and 250 feet per second. When the outletvelocity is maintained at less than about 50 feet per second the polymerpowder tends to accumulate on the heating surface and plug the line. Thehigh turbulence under these conditions results in the rapid and uniformevaporation of substantially al1 of the monomer leaving a polymer powderdry enough to fluidize readily. The mixture is discharged throughconduit 93, connected either radially or tangentially to primaryseparator 94.

The powder settles to the bottom of 94 which is heated sufficiently tomaintain a temperature that will vaporize any residual monomer occludedor adsorbed in the polymer powder. A stream of aeration gas isintroduced to the bottom of the vessel 94 through Valve 120 online 121to maintain a fluid bed and tov act as a stripping medium to removevaporized monomer. The use of nitrogen for this purpose is shownalthough any other gas which is non-reactive in the system may be used.

In order to insure a powder particle size distribution that will uidizereadily and to prevent accumulation of polymer on the walls lof theseparator, a portion of finished polymer which has been extruded andreground to coarse particle size is introduced (means not shown) intothe coarse polymer hopper 109. It ows from the hopper through bottomvalve 123 into line 114 where it is picked up in a stream of nitrogenadmitted to the line through valve 119 and is carried to a point inprimary separator 94 such that it will thoroughly mix with the powderdischarged from the ilash dryer.

A portion of the polymer product is Vallowed to mix with the coarsepowder in hopper 109 and is recycled to the primary hopper 94. Thispermits control of the rate of powder flow in the bottom of 94 and thusassists in the ability to maintain a good iluid condition. The netpolymer product is elutriated from hopper 109 in a stream of nitrogen orother suitable gas introduced into the bottom part of hopper 109 throughvalve 122 in suicient quantity to provide the required elutriatingvelocity in that vessel and discharged throughline 111 to storage hopper112.

Vaporized monomer passes overhead from separator 94 through line 96 tolters 97 and 98. Valves 99, 101, 102 and 103 are used to shut downeither of the filters for cleaning or repair. Vaporized monomer free ofpolymer but containing nitrogen ilows through line 130, compressor andcondenser 131 into accumulator 132.` This accumulator is held undersufficient pressure, by nitrogen ilow through valve 137, to How -throughline 134 valve 135 and line 136 to line 74 and so back to the reactorfeed accumulator. To control the concentration of contaminants in therecycle monomer a part of the recycle is bled off through valve 138 andis pumped by pump 133 to accumulator 22 for monomer purification.Primary separator 94 and polymer-hopper 109 are maintained under slightpressure with nitrogen gas. The nitrogen is removed from the equipment,is recovered and recycled by means not shown.

While the process of this invention has been described above and inFigure l of the drawing, in one of its preferred embodiments, it will beadvantageous at times to incorporate some of the aspects of theinvention in other processes. Thus, Figure 2 of the drawing illustratesthe use of the flash dryer in an auto-clave type process. According toFigure 2 of the drawing triuorotrichloroethane '83' to polymerizationreactor 82.

' clave.

-reactors -due to local time-temperature pockets. higher. yield of moreuniform quality polymer is, therefore, produced.

and methanol-zincfslurry are introduced into 'the devclorination reactor.through conduit'll. TheV reaction is initiated in the rea'ctorlbyVheating with steam. .Oncethe reaction has started cooling liquid iscirculated through coils positioned on the reactor .to control.temperature.

Conventional vstirrer16 is used to circulate .the reactants.

The temperature in the reactorlr is adjusted so that monomer andentrained methanol pass overhead through dephelagmator wherein asustantialy portion of the methanol is condensed and returned to thereactor. Contaminated monomer is passedthrough conduit 19 to accumulator22. Conventional cooler 2l) condenses the vaporous monomer prior to itspassage to the accumulator.

The purification of the monomer contained in accumulator V22. iseffected in a manner identical with that described in Figure 1 of thedrawing. The various components employed in the purification process inFigure 2 of the drawing 4are numbered identically with the components ofFigure 1 'of the drawing. Reference may therefore, be made to Figure 1of the drawing in order to follow the process described in Figure 2.

' Prior to its introduction into the polymerization reactor, purifiedmonomer is held in accumulator 75. T he puried monomer ispassed from theaccumulator through conduit An organic peroxide preferably a halogenatedacyl peroxide such as trichloroacetyl peroxide is introduced into thereaction zone through conduit 86. The polymerization reactor 82illustrated in the drawing, is a preferred type Ofanto-clave reactorthat is, a three stage horizontal reactor. Other .types of auto-clavereactors may be substituted for that shown in the drawing, such asvertical single stage auto- The use of such other auto-claves affords noadvantage over the three stage type and has' instead some disadvantages.

The polymer produced in reactor 82 forms'. as a particulate4 suspensionin the monomer and is present in an amount'not exceeding-about 12% byweight and preferably about 6%. The monomer-polymer slurry is`withdrawnfrom the end of the polymerization reactor and is passed through conduit91 to a ash dryer. Conventional -pump 90 is used to control the feedrate of the monomerpolymer slurry to the flash dryer. The separation ofpolymer from monomer by means of the ash dryer and its auxiliaryequipmentl is described at length above inconnection with the process ofFigure l of the drawing. Reference numerals used on-each of the guresare identical-so that cross-referencing will be simplified.

The process of this invention has been described above in specified flowchannels from feed to product. As was indicated lin this description,the significant aspect of the invention resides in the use of elongatedtubular reaction 'zones-preferably angularly disposed in continuousdownward ow. By means of this arrangement various temperature sensitivereactions are conducted with adequate mixing and opportunity for contactwith heating or coolingl surfaces so that optimum -temperature'controlis attained.

-'With optimumy temperature control the reaction may be conductedat-higher average temperatures and higher conversion rates withoutgetting the undesirable side reaction products 'which are'unavoidable instirred auto-clave type lA At the same time the arrangement permits theuse of velocities lowA enough'sothat pressure drop, in the elongatedpath necessaryto the required contact time, will avoided because ofthedanger of stoppage due to build-up of'solids while pipe vdiameterssubstantially in excess of "-2 iuchesygenerally do not enablesatisfactory-temper- '8 ature control. For example, the dechlorinationreactor may comprise a tube between about a 0.25 inch pipe and about 2inches preferably between about 0.5 and about 1125 inches in diameter.The length of the dechlorinavtion reaction zone may be between about 30feet and about 120 feet preferably between about 60 feet and about 100feet. The polymerization reaction zone likewise is made of a pipebetween about 1A inch and about 2 inches in diameter preferably betweenabout 0.5 and about 1.25 inches but of considerably longer length due tothe nature of the reaction which occurs therein. Thus, thepolymerization reactor for the described reaction is between about 5,000feet and about 25,000 feet in length, prefer- `ably between about 10,000feetand about 20,000 feet. Because of its length the polymerizationreactor is preferably arranged in theform of a coil or helix. lThe coilis disposed so as to securey the necessary velocity of the reactants inthe reaction zone. Generally, the coil is so arranged thatthe reactantsmove through ity at a velocity preferably between about 0.5 foot andabout 4 feet per second. The size of the flash dryer is based upon themaximum output of the polymerization zone. Theash dryer comprises anelongated tube or a pipe between about 0.25 and about 2 inchespreferably between about 0.5 and 1.25 inches in diameter and betweenabout 20 and about 100 feet in length.

ln order to more clearly illustrate the present invention, its use willbe described with reference to particular operating conditions, althoughitis believed quite obvious that dimensional changes in equipment andquantitative and qualitative changes in material input and output may bemade based on the data given herein. The dehalogenation reactor which isdescribed herein, is made of a footl length of 1 inch pipe positioned asan'angular downward sloping unit so vthat gravity will assist a Velocityof from 2 to 6' feet per second to carry the zinc `powder through theline. The reactor is situated in-.a temperature controlled bath which ismaintained at about C.

`In order to get 100% conversionof the Freon.ll3"to monomer aconsiderable vexcess of zinc, about 10%, must be available, and toprovide this condition zinc is recycled from the product separator tothereactor heater as a slurry suspension in a liquid mixture of zincchloride and methanol. An excess, Vabout'5%, of monomer is preferablyadded to make up for losses. Methanol is added as required. In order tomaintain the desired velocity, one-tenth of the total hourly quantity ofreactants and the total quantity of methanol are passed throughthereactor in .one pass. Ten passesperfhour making .upon thev requiredhourly input and output. The feed per pass consists of:

From` the reactor the mixture owsto theseparatorsettler tower'where themonomerV product about 163 pounds'plus a small fractionof methanolisashed overhead. A conventional overheadreuxl system serves'to controlthe quantity of methanol in the overhead stream. The liquid slurrybottoms from the separator section flows into the settler section wherethe unreacted zinc settles in morey concentrated slurry with liquid zincchloride' and 'methanol and isv pumped' therefromasrecycle to thereactorheater. To; control theI concentration of ziucchlo- 'ride in thev4'circulating stream a; portion "mixed with Dmethanol vis vwithdrawn as'rarleeanted liquidffronr'thetop .described above. the `'system .is suchthat the zinc chloride is held in the ,of the settler. Themethanol isrecovered from the zinc about 1 pound, in the product and recyclestreams which areconsidered ,in the recovery and puriiication equipmentThe temperature control throughout liquid phase. Substantially puremonomer is accum- .,ulated inaccumulator 72.

Polymerization of the accumulated monomer, in this instance, is effectedin a polymerization reactor which comprises a 1% inch standard pipeapproximately 16,540 feet long, arranged in a helix or coilapproximately 31 feet'in diameter. The coils are so disposed that thevelocity of the reactants in the polymerization reactor is betweenabout- 0.3 foot-.and about 4 feet per second preferably about 0.8 footper second.. The 163 pounds per hour of produced monomer, is added toabout 2600 pounds ,per hour of recycled monomer in an accumulator 75.2763 pounds per hour of monomer are passed through the polymerizationreactor together with about 8 pounds of trichloroacetyl peroxidepromoter dissolved in a suitable solvent such astrichloromonofluoromethane which is introduced at at least one pointalong the polymerization reactor. In this instance, conditions areadjusted so as to effect a 6% conversion of the monomer to polymer.Thus, about 160 pounds per hour of polymer suspended in approximately600 pounds perv hour of monomer leave the polymerization reactor and arepassed to ash dryer 92.

In the process of this example, the flash dryer is a 1 inch pipeapproximately 40 feet in length. The monomer-polymer slurry isintroduced into the ash dryer at a velocity suiicient to avoid settling.A pressure reduction between the polymerization reactor and the flashdryer controls the flow rate. Temperature of the flash dryer ismaintained at about 100 C. by means of low pressure steam. The polymerleaves the ash dryer in the form of a uidized powder dispersed inmonomer vapor, at a velocity of about 200 feet per second and is passedinto primary separator 94 where a major portion of the monomer isseparated from the polymer and ow overhead through lters to the recyclesystem.

The polymer product settles out and is maintained by a heat source at atemperature high enough to evaporate any residual monomer. A strippingmedium such as nitrogen is used to maintain an eicient strippingvelocity in the fluid bed. A recycling stream of coarse ground polymerproduct is mixed with the reactor product in the primary separator toassist in maintaining a particle size distribution suitable for goodfluidization in the bottom bed. This quantity of coarse ground polymermay be as much or more than the polymer product, i. e., between about0.5 and about 2 times.

The mixture of powder ows through a control valve from the bottom of theprimary settler, is picked up in a stream of nitrogen and carried to thecoarse polymer hopper where the fine polymer product is carried overheadin suspension in nitrogen and the coarse polymer with some lines settlesout to be recycled to the primary separator.

The ash dryer shown in Figure 2 of the drawing is similar to thatdescribed above, with reference to Figure 1 of the drawing. Thus, aone-inch pipe 40 feet long, was maintained at a temperature of about 100C. by means of low pressure steam. In this example, about 170 pounds perhour of monomer is withdrawn from dechlorination reactor 14 and ispuried as described above. The produced monomer together with recycledmonomer amounting to about 2680 pounds per hour is passed throughconduit 83 to polymerization reaction 82 together with about 7.6 poundsper hour of a solution of trichloroacetyl peroxide intrichloromonouoromethane. About 170 pounds per hour of solid polymersuspended in liquidmonomer is withdrawn through conduit 91 passed bymeans of pump 90 `to flash dryer. Separation ofthe monomer and recoveryof the. polymer is electedas described with reference to Figure 1 of thedrawing.

Various modifications and alterations of the process of this inventionwill be apparent to those skilled in the art and may be used withoutdeparting fromthe vscope of this invention.

Having thus described my invention, I claim:r

1. A process for the production of triuorochloroethylene monomer whichcomprises, introducing triuorotrichloroethane, methanol and nely dividedmetallic zinc, to a preheating zone in which they are preheated to atemperature between about 90 C. and `about 180A C., passing thesepreheated materials from said preheating zone into a dechlorinationzone, owing said materials through said dechlorination zone in a helicalpassage having a pitch of between about 20 degrees and about 60 degreesfrom the horizontal, having a length between about 60 feet and about 100feet and a diameter between about 0.5 inch and about 1.25 inches,maintaining said dechlorination zone at a temperature below thetemperature of said preheating zone and,` between about 50 C. and about150 C. under conditions such that triuoro trichloroethane isdechlorinated to trifluorochloroethylene, said materials ilowingdownwardly through said dechlorination zone at a velocity between about2 feet and about 6 feet per second and maintaining turbulent flow,removing from the bottom portion of said dechlorination zone adechlorination eluent comprising trifluorochloroethylene, methanol andunreacted zinc, passing said dechlorination effluent to a monomerseperation zone, withdrawing a liquid bottoms from said monomerseparation zone comprising unreacted zinc and methanol, recycling saidliquid bottoms to said preheating zone, removing from the upper portionof said monomer separation zone, a vaporous effluent comprisingtrifluorochloroethylene together with impurities formed in saiddechlorination zone, removing said impurities from saidtrifluorochloroethylene in a purication zone land recovering saidtrifluorochloroethylene as a product of the process.

2. A process for the production of triuorochloroethylene monomer whichcomprises introducing triuorotrichloroethane, methanol and finelydivided metallic zinc into a preheating zone in which they are preheatedto a temperature between about C. and about 250 C., passing thesepreheated materials from said preheating zone into a dechlorinationzone, owing said materials downwardly through said dechlorination zonein a tubular passage disposed at an angle between about 5 and about fromthe horizontal, having a length between about 30 feet and about 120 feetand a diameter between about 0.25 and about 2 inches providing a highsurface to volume ratio, maintaining said dechlorination zone at atemperature between about 40 C. and about 175 C. under conditions suchthat triuorotrichloroethane is dechlorinated to triuorochloroethylene,flowing said admixture downwardly through said dechlorination zone at avelocity between about 0.5 foot and about l0 feet per second providingturbulent ow, removing from the bottom portion of said reaction zone aneilluent comprising triuorochloroethylene, methanol and unreacted zinc,passing said dechlorination efuent to a monomer separation zone,withdrawing a liquid bottoms from said monomer separation zonecomprising unreacted zinc and methanol, recycling said bottoms to saidpreheating zone, removing from the upper portion of said monomerseparation zone a vaporous effluent comprising trilluorochloroethylenetogether with impurities formed in said dechlorination zone, removingsaid impurities from said triuorochloroethylene in a purification zoneand recovering said triuorochloroethylene free of impurities as aproduct of the process.

'.1 1 "3. 'A process"for^the production `of tr'iuorochloroethylenemonomer' which" comprises introducing triuorotrichloroethane,`a suitablesolvent and anely divided metallic dehaloge'nating' agent to a`preheating zone in l which they are preheated to a temperature betweenabout '75 C. and about`250` C.,'passing thesepreheated materialsfromsaid preheating zone to a dechlor'ination zone,

owing said' materials 'downwardlyth'rough' said dechlorination zone in atubular passage, said' I'zvassagehavingl a high surface to volume ratio,having a length of at" least about 30 feet and a diameter of betweenabout 0.25

yirl/ches and about two inches, maintaining said dechlorination zone ata temperature between about 0 C. and about 200 C. under conditions suchthat triuorotri- Ichloroethane is dechlorinated totriuorochloroethylene, said'materials flowing through said tubularpassage at a velocity of between about 0.5 and about 10.0 feet persecond at an angle' from the horizontal of between about i5 and about 60|degrees to provide turbulent ow, removing from said dechlorination zonean euent cornprising triuorochloroethylene solvent and unreacted de-'halogenatingv agent, passing said effluent to a monomer 'separationzone, withdrawing a liquid bottoms from 'said monomer separation zonecomprising solvent and unreacted dehalogenating agent, recycling atleast a portion of said liquidV bottoms to said preheating zone removingfrom the upper portion of said monomer sep- 'aration zone. a vaporouseuent comprising triuorochloroethylene' as a product of the process.

4. A process for the'v production lofi pei'uorochloro- 'olefin monomerwhich comprises'introducing as reactants, a' 'peruorochloroparancontaining `at 'least vthree chlorineatoms and at `least onechlorine"atom oneachof two adjoining carbon atoms and "a'fnelyydividedlmetallicdehalogenating "agent to a dechlorination zone,"`owing said reactantsdownwardly through said dechlorination zone in a tubularpassage 'havinga*highsu'rface"'to Vvolumeratio,"having alengthoatleast about 30' feetand a diameter of between about 0.25'inchand'about 'two inches, saidreactants owing through 'said 'dechlorination zone at avelocity'of atleast about 0.5` foot per second and at an angle from thel horizontalofbetween 5 and about 90 degreesvto `provide 'turbu1entow, said spoudingperuorochloroolen during its passage through said dechlorination'zone,and recovering said vperlluorochloroolen as a product of the process.

References'Cited in the le of 'this patent UNITED STATES :PATENTS PatentNoo 2,877,275 March lO, 1959 Joseph Warren Jewell It is hereby certifiedthat error a of' the above numbered patent .requiring c Patent shouldread-'as corrected below.

ppears in the printed specification orrection and that the said LettersColumn l, line 26, for "in the" reed into the ma 4 4, for "packe-ted"read im jacketed Lm read n 5o g column 3, line gv line 50, for thenumeral "59" column 77 line 9, for "sueieriiel" read substantiel nu,

Signed and sealed this 29th day of March 19600 (SEAL) Attest:

KARL E, AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

1. A PROCESS FOR THE PRODUCTION OF TRIFLUOROCHLOROETHYLENE MONOMER WHICHCOMPRISES, INTRODUCING TRIFLUOROTRICHLOROETHANE, METHANOL AND FINELYDIVIDED METALLIC ZINC, TO A PREHEATING ZONE IN WHICH THEY ARE PREHEATEDTO A TEMPERATURE BETWEEN ABOUT 90* C. AND ABOUT 180* C., PASSING THESEPREHEATED MATERIALS FROM SAID PREHEATING ZONE INTO A DECHLORINATIONZONE, FLOWING SAID MATERIALS THROUGH SAID DECHLORINATION ZONE IN AHELICAL PASSAGE HAVING A PITCH OF BETWEEN ABOUT 20 DEGREES AND ABOUT 60DEGREES FROM THE HORIZONTAL, HAVING A LENGTH BETWEEN ABOUT 60 FEET ANDABOUT 100 FEET AND A DIAMETER BETWEEN ABOUT 0.5 INCH AND ABOUT 1.25INCHES, MAINTAINING SAID DECHLORINATION ZONE AT A TEMPERATURE BELOW THETEMPERATURE OF SAID PREHEATING ZONE AND BETWEEN ABOUT 50* C. AND ABOUT150* C. UNDER CONDITIONS SUCH THAT TRIFLUOROTRICHLOROETHANE ISDECHLORINATED TO TRIFLUOROCHLOROETHYLENE, SAID MATERIALS FLOWINGDOWNWARDLY THROUGH SAID DECHLORINATION ZONE AT A VELOCITY BETWEEN ABOUT2 FEET AND ABOUT 6 FEET PER SECOND AND MAINTAINING TURBULENT FLOW,REMOVING FROM THE BOTTOM PORTION OF SAID DECHLORINATION ZONE ADECHLORINATION EFFLUENT COMPRISING TRIFLUOROCHLOROETHYLENT, METHANOL ANDUNREACTED ZINC, PASSING SAID DECHLORINATION EFFLUENT TO A MONOMERSEPARATION ZONE, WITHDRAWING A LIQUID BOTTOMS TO SAID MONOMER SEPARATIONZONE COMPRISING UNREACTED ZINC AND METHANOL, RECYCLING SAID LIQUIDBOTTOMS TO SAID PREHEATING ZONE, REMOVING FROM THE UPPER PORTION OF SAIDMONOMER SEPARATION ZONE, A VAPOROUS EFFLUENT COMPRISINGTRIFLUOROCHLOROETHYLENE TOGETHER WITH IMPURITIES FORMED IN SAIDDECHLORINATION ZONE, REMOVING SAID IMPURITIES FROM SAIDTRIFLUOROCHLOROETHYLENE IN A PURIFICATION ZONE AND RECOVERING SAIDTRIFLUOROCHLOROETHYLENE AS A PRODUCT OF THE PROCESS.